1. Field of the Invention
The present invention relates generally to a processing arrangement utilizing laser beams. Particularly, the present invention relates to a laser processing arrangement which can accurately sense a temperature of a material being irradiated by a laser beam for accurate adjustment thereof to prevent defective processing operation.
2. Description of the Prior Art
Laser processing arrangements are known in the art which utilized laser beams and temperature sensors for processing of work pieces of various types of material. One such laser processing arrangement is exemplified by Japanese Patent Application, first publication (unexamined) 63-190115. Referring to FIG. 4, this laser processing arrangement 101 includes a laser oscillator 102 which outputs a laser beam 103, a reflecting mirror 105 from which the laser beam 103 is reflected to a collimating lens 105. Numeral 106 represents a work piece to be processed by the arrangement. The prior art arrangement further includes a sensor 107 associated with a temperature detecting means 108 for detecting a temperature in the vicinity of the work piece. The temperature detecting means 108 is associated with a control unit 109 for effecting automatic control of the laser oscillator 102.
Furthermore, the work piece 106 is positioned on a processing table 110 which is rotatably movable on a lengthwise horizontal axis by a first servo motor 111 and a width horizontal axis by a second servo motor 112. The first and second servo motors 111 and 112 are controlled by the control unit 109 for moving the work piece 106 relative the laser beam 103.
However, in some cases, a surface reflectivity of the work piece 106 is enough to prevent sufficient heating of the work piece 106 during processing. In such cases, it is necessary to include a laser absorbing layer 113 (such as a graphite based material for example) to insure sufficient heating of the work piece 106.
It has been observed by the inventors of the present invention, that a vibratory field including a P component parallel to the plane of incidence and an S component perpendicular to the plane of incidence develops in laser processing, these components may be utilized to stabilize a laser irradiation process according to a set direction of incidence which. This process is disclosed in Japanese Patent Application No. 2-132291. However in order to utilize the above principles a high accuracy is required in sensing an actual surface temperature of an irradiated area of the work piece 106. However, since, in many cases, a laser absorbing layer 113 is employed during processing, accurate monitoring of an actual surface temperature is not possible and stable laser processing is inhibited.